The present invention relates to the production of edible, low cost, bland tasting, high protein textured vegetable products derived from proteinaceous plant materials, such as soybeans, peanuts, and other legumes and nuts, which products resemble animal tissue when hydrated.
The recent widespread interest in textured vegetable products was generated to a large extent by the hope that such products could solve the problem of low protein diets in the undeveloped countries of the world. Experience had shown that in many of these areas the people would not accept protein rich legumes in their natural state, either whole or in meal form. To them beans and the like were the food of the food and where looked down upon. In such areas, meat is the food of the wealthy, a status food desired by everyone. Therefore texturized vegetable protein products were developed to provide a high protein food source which would look, chew and taste like meat and therefore would be accepted by the people.
Paradoxically, the previous commercial processes for producing texturized vegetable protein products were not suited to the conditions which exist where the food is needed. The equipment is quite expensive and complex and requires substantial electrical energy. As a result, the cost of such products, while considerably less than that of meat, was still too high for the great majority of people in the developing countries.
Even these prices could be achieved only when the high intitial equipment cost was spread over a high production volume. The high energy needs dictated that these processes could be carried out only in industrialized areas and therefore an extensive distribution system would be required to get the products to those people who needed it most. These processes could not be practiced on a small scale within remote villages where the only energy sources might be manual labor and a cook stove.
As a result, texturized vegetable protein is now produced almost exclusively as a lower cost meat substitute for sale in the protein-rich, developed areas of the world. Its function is not to supply protein to a deficient population, but to reduce the cost of protein to a well fed population.
Most of the textured vegetable protein products which have been commercially made in the past have been made by three general procedures. Each of these procedures utilize equipment which is expensive and requires a sophisticated source of electrical power. In the first procedure, protein isolates are produced and these isolates are extruded and spun into fibers. The fibers are formed into pieces or bundles by use of a suitable binder material to form meat-like chunks having a protein content of up to about 90%. An example of this procedure is found in U.S. Pat. No. 3,118,959.
In the second procedure the proteinaceous vegetable material, in meal form, is compacted in a high pressure extruder and the extrudate is broken into chunks. These chunks have a meat-like texture when hydrated in boiling water. An example of this process is disclosed in U.S. Pat. No. 4,057,656. At this stage, the product has the same protein content as the starting vegetable protein material. The protein content of this product can be increased by subjecting the chunks to hot or boiling water for about 11/2 hours to dissolve out soluble carbohydrates. An example of a process including the protein concentrating step is disclosed in U.S. Pat. No. 3,912,824.
In the third commercial procedure, for forming textured vegetable protein, proteinaceous vegetable material, such as soy meal, is mixed with water to form a dough. This dough is extruded under high pressure and heat to produce an expanded product having a lattice network structure. An example of this type of procedure is given in U.S. Pat. No. 3,940,495 wherein the pH of the dough is controlled within the range of 5 to 12 to achieve a satisfactory fibrous structure in the expanded product. This type of procedure produces a product of up to about 50% protein if soy meal is used as the starting material. To produce products of higher protein content, a soy concentrate (70% protein) or soy isolate (90% protein) can be mixed with the soy meal.
A soy concentrate is made by either (1) treating the soy meal with an aqueous solution of an organic solvent which dissolves out soluble carbohydrates, or (2) mixing the soy meal with many times its weight of an aqueous acid solution having a pH in the minimum protein solubility range of 4-5 to leach out soluble carbohydrates, or (3) mixing the soy meal with many times its weight of an aqueous solution containing alkaline earth cations to leach out soluble carbohydrates without dissolving the proteins.
Each of the aforementioned commercial texturing procedures has a relatively high energy requirement. This is particularly true for those products which have an enhanced protein content. To produce such products by the previous commercial procedure requires that two separate processes be used. One process is necessary to enhance protein content and a second process is required to produce texturization. When the protein concentration is achieved before texturization, the starting material is processed to produce soy isolate or concentrate and the isolate or concentrate is texturized by a second process. When the starting material is texturized first, a high pressure extruder-compactor is used to produce texturized chunks, and the chunks of the compacted material must then be subjected to extended cooking to leach out carbohydrates.